Electroless plating is a method by which a metal plated layer is formed on an object to be plated through an oxidation-reduction reaction of a metal, and since plating is possible irrespective of the shape of a product, and since after undergoing a particular pretreatment process, even an insulating material may be plated, electroless plating is used in various industrial sectors.
The importance in the materials and components industry of surfaces plated through electroless plating is steadily increasing, such plated surfaces being used in various areas of packaging as a mounting surface or a junction interface, and the like, of micro elements having a high density. Recently, in accordance with efforts to produce electronic products that are lighter, smaller, and have a higher functionality, there has been a demand for increasing the density and narrowing the pitch of internal circuits, and consequently, the need is increasing for an electroless plating method that is not affected by plating area or product shape, and has a small variance in the thickness of the plated layer.
In particular, since a plating film formed through the electroless nickel plating method may control the amount of phosphorous that is precipitated and formed through a eutectoid reaction, the plated layer including an amorphous metal alloy may be formed, the plated layer having a uniform surface may be obtained, and the plated layer having excellent corrosion resistance and wear resistance, and the like, may be formed. Thus, electroless nickel plating is being widely applied as the plating technique used in the final surface treatment of automobiles, precision machine components, semiconductors, and printed circuit boards (PCB), and the like. Moreover, the areas of application are becoming broader, such as being used for treating failures in soldering joints in printed wiring boards or in the primary treatment of compact disks (CD) or hard disk drives (HDD).
In particular, unlike a rigid printed circuit board in which the materials are hard, since a flexible printed circuit board that uses an insulting film is thin and flexible, and thus enables smaller and lighter electronic components, the quantity of flexible printed circuit boards being used is increasing. When the flexible printed circuit board is used, since complex electronic circuits may be realized on the flexible insulating film, a useful solution may be provided with respect to improving quality, reducing size, and narrowing the pitch of the line width in electronic products, and thus the range and quantity used in mobile phones, digital cameras, notebook PCs, smartphones, tablets, PCs, and the like, is increasing.
As such, as the quantity of flexible printed circuit boards being used increases, there is a need for research about methods for plating flexible printed circuit boards. A typical electroless nickel plated layer has a high hardness, and excellent corrosion resistance and wear resistant properties, but has a poor percent elongation such that fracturing may easily occur, and thus there is a limitation to the application of flexible printed circuit boards. Moreover, since commercial high-flexibility electroless nickel plating solutions lack stability and the properties of the plated layer change according to the number of times the solutions are used, there is a limitation in that the lifetime of the plating solution is short.